var result: FileData = (<any>cursor).value;

        if (result && result.properties) {

          recipient.file(result.path, result.properties);

        }

        cursor.continue();

      };

    }

    migrate(

      editedUTC: number,

      filesByName: { [name: string]: { [name: string]: string; }; },

      callback: (error: Error, updater: attached.UpdateStorage) => void){

      var transaction = this._db.transaction(['files', 'metadata'], 'readwrite');

      transaction.onerror = (errorEvent) => callback(wrapErrorEvent(errorEvent, 'migrate: transaction'), null);

      var filesStore = transaction.objectStore('files');

      var clearFiles = filesStore.clear(); 

      clearFiles.onerror = (errorEvent) => callback(wrapErrorEvent(errorEvent, 'migrate: objectStore(files)-clear'), null);

      clearFiles.onsuccess = (event) => {

        var metadataStore = transaction.objectStore('metadata');

        var clearMetadata = metadataStore.clear();

        clearMetadata.onerror = (errorEvent) => callback(wrapErrorEvent(errorEvent, 'migrate: objectStore(files)/clear-objectStore(metadata)-clear'), null);

        clearMetadata.onsuccess = (event) => {

          var editedUTC = Date.now();

          var putEditedUTC = metadataStore.put({ property: 'editedUTC', value: editedUTC });

          putEditedUTC.onerror = (errorEvent) => callback(

            wrapErrorEvent(errorEvent, 'migrate: objectStore(files)/clear-objectStore(metadata)/clear-put(' + editedUTC+')'),

            null);

          putEditedUTC.onsuccess = (event) => {

            var filenames: string[] = [];

            for (var k in filesByName) if (filesByName.hasOwnProperty(k)) { 

              filenames.push(k);

            }

            if (!filenames.length) {

              var update = new UpdateStorage(this._db);

              callback(null, update);

              return;

            }

            var completedFiles = 0;

            var anyError = false;

            filenames.forEach(file => {

              if (anyError) return;

              var fileData = { path: file, properties: filesByName[file] };

              var putFile = filesStore.put(fileData);

              putFile.onerror = (errorEvent) => {

                if (anyError) return;

                anyError = true;                

                callback(wrapErrorEvent(errorEvent, ''), null);

              }

              putFile.onsuccess = (event) => {

                completedFiles++;

                if (completedFiles === filenames.length) { 

                  var update = new UpdateStorage(this._db);

                  callback(null, update);

              }

            });

          };

        };

      };

    }

  }

}